Electrode physiology catheters applying radio frequency energy ablation have been used to treat heart arrhythmias caused by aberrant electrical activity in the heart tissue. In particular, the catheters are configured with tip electrodes that deliver RF energy to the heart tissue to heat and kill it by ablation. The scarred tissue no longer conducts the errant excitation waves and effectively isolates these waves from other areas in the heart.
For tissue ablation, there are several motivations to deliver the RF energy through the catheter tip, including i) the natural tendency for the tip of the catheter to contact the wall of the heart chamber, ii) the physician's ability to manipulate the tip to the desired location and hold it in place with sufficient pressure to facilitate both stability and RF current flow to the tissue, and iii) the desire to afford sufficient surface area for tip/tissue interface cooling by blood flow around the tip electrode to avoid cutting or charring the tissue. Given the foregoing factors, the tip electrode of the catheter is often the instrument of choice for RF ablation.
Irrigated tip electrode catheters are a known improvement for their ability to cool the tip/tissue interface and/or dilute the adjacent blood by irrigation. Such catheters are configured to emit a cooling liquid, such as normal saline or dextrose/saline solution, out tiny holes in the tip electrode at or near the tip/tissue interface. The liquid cools the tip tissue interface and lowers the adjacent “hematacrit,” both of which in turn greatly reduce thrombus formation and charring at the interface.
The design of hole patterns can be crucial for efficient irrigation, that is, the achievement of sufficient cooling without seriously loading the patient with coolant. With proper design of the hole patterns, it is possible to achieve efficient irrigation with insignificant local blood dilution. Accordingly, it is possible to achieve a much improved RF lesion with greatly reduced danger of thrombus formation from charring.
However, a challenge with irrigated tip electrodes is the need to isolate the irrigation liquid from the electrical components attached to and imbedded in the tip electrode, which can include the lead wires, electrical or electromagnetic sensors and/or temperature sensors. A further compounding challenge is the spatial confinement in the tip region which mandates efficient use of the limited space to house the above components. The fabrication of the irrigated tip electrode therefore involves multiple factors, including combining irrigation control for maximum cooling efficiency, sealing off irrigation components from the electrical components, providing sufficient space in the tip electrode for all these components, and avoiding detachment of the tip electrode from the catheter.
It is therefore desirable to provide a catheter with efficient and effective irrigation such as where irrigation holes are situated around the extreme distal end of the tip electrode and the irrigation paths in the tip electrode are of generally equal and short lengths. It is further desirable that such a catheter provides for separate and isolated compartments between the irrigation and electrical components. It is also desirable to provide a method of fabricating such a catheter where there is irrigation control for maximum cooling efficiency, the irrigation is sealed off from the electrical components, there is sufficient space to house all the irrigation and electrical components and/or the tip electrode is securely attached to the catheter.